Not sure how penetrated your stain is, but I have this problem often, either from my herbal baths or from Henna.
I don't use bleach, but have found that scrubbing with baking soda or a borax soak works well. One of our tubs is in need of a refinish and has lost almost all enamel gloss. This is the one I use borax for, and let it sit for about 30 minutes (diluted with water.) Give it a try?
Hope it works!
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Constantly typing as if I am
but am not.
Forgive my ramblings. I process through typing.
That thing says I am an ENFP. It also says I am an ENFJ.